@patch("caching.worker.os")
    @patch("caching.worker.Worker._delete_directory")
    @patch("caching.worker.Worker.__init__")
    def test__generate_directory(self, mock_init, mock_delete_directory, mock_os):
        # setup return values for function to pass
        mock_init.return_value = None
        mock_os.path.isdir.return_value = False

        # initiate the worker and run the function
        test = Worker()
        test.base_dir = "test dir"
        test._generate_directory()

        # check that the checking of path has been done once with the base dir
        mock_os.path.isdir.assert_called_once_with(test.base_dir)

        # check that the mkdir function is called once with the base dir
        mock_os.mkdir.assert_called_once_with(test.base_dir)

        # setup return values for the directory to already exist
        mock_os.path.isdir.return_value = True

        # check that it raises an exception because of this
        with self.assertRaises(Exception):
            test._generate_directory()

        # check that the mkdir has still only been called once
        mock_os.mkdir.assert_called_once_with(test.base_dir)

        # check that the isdir function has been called twice
        self.assertEqual(2, len(mock_os.path.isdir.call_args_list))

        del test

        mock_delete_directory.assert_called_once_with()